Whisk broth, tomato paste, vinegar, sugar, soy sauce, oil, cornstarch and red pepper in a small bowl.Advertisement
Ingredient Note: Chinkiang is a dark, slightly sweet vinegar with a smoky flavor. It is available in many Asian specialty markets. If unavailable, balsamic vinegar is an acceptable substitute.
People with celiac disease or gluten-sensitivity should use soy sauces that are labeled "gluten-free," as soy sauce may contain wheat or other gluten-containing sweeteners and flavors.